Spontaneous emergence of non-planar electron orbits during direct laser acceleration by a linearly polarized laser pulse

Arefiev, A. V. and Khudik, V. N. and Robinson, A. P. L. and Shvets, G. and Willingale, L. (2016) Spontaneous emergence of non-planar electron orbits during direct laser acceleration by a linearly polarized laser pulse. Physics of Plasmas, 23 (2): 023111. ISSN 1070-664X

Abstract

An electron irradiated by a linearly polarized relativistic intensity laser pulse in a cylindrical plasma channel can gain significant energy from the pulse. The laser electric and magnetic fields drive electron oscillations in a plane making it natural to expect the electron trajectory to be flat. We show that strong modulations of the relativistic gamma-factor associated with the energy enhancement cause the free oscillations perpendicular to the plane of the driven motion to become unstable. As a consequence, out of plane displacements grow to become comparable to the amplitude of the driven oscillations and the electron trajectory becomes essentially three-dimensional, even if at an early stage of the acceleration it was flat. The development of the instability profoundly affects the x-ray emission, causing considerable divergence of the radiation perpendicular to the plane of the driven oscillations, while also reducing the overall emitted energy. (C) 2016 AIP Publishing LLC.